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How concentration of reactants affect rate of reaction

Answer Text:
How concentration of reactants affect rate of reaction:
- Increase in concentration of one of the reactants increases the rate of the reaction;
Reason:
- Higher concentration results in a greater probability of collision hence a higher rate of reaction
Example: reaction between Mg(s) and 2M and 4M hydrochloric acid.
- The maximum volume of a gas collected in both experiments is the same because the number of moles of HCl is the same
- Curve for 4M HCl is steeper indicating a faster rate because the acid is more concentration
- The 4M HCl contains more #H^(+)# ions per unit volume than 2M HCl. This reaction takes a shorter time to go to completion
- The start of the flat part of the curve indicates the end of the reaction;

Note: Rate of reaction can also be verified by measuring the rate of disappearance of reactants per unit time.
- Reactants with 4M HCl will disappear faster;
- Curve for a faster reaction rate is always to the left of the reference curve;